The nature of electrical loads and the mixture of generation sources on medium voltage distribution lines in utility power networks is changing due largely to increased presence of solar generation plants and other distributed generation (DG) equipment. While these new power sources are a very positive development, they can create electrical problems at specific locations on distribution lines, which has increased the need by utilities for targeted dynamic voltage regulation solutions on distribution lines, often far from substations.
Switched capacitor banks and/or tap changing voltage regulators may be installed along medium voltage distribution lines; however, they are often not a sufficient solution to the electrical problems that need to be addressed by utilities caused by DG power sources. Conventional medium voltage STATCOMs may provide a complete solution to the electrical problems faced by utilities; however, given their size, footprint, and collateral connection equipment required, they must be ground-based systems installed within a substation. This prevents their widespread adoption into distribution grids and critically precludes them from use for voltage correction at the optimum points of connection on such grids. Existing medium voltage STATCOMs supplied by companies such as AMSC, General Electric, ABB, S&C Electric, and Mitsubishi, are contained in ground mounted enclosures or installed within a ground mounted building, in both cases within a substation. Many of these STATCOMs use low voltage power electronics, which requires additional dedicated external equipment (e.g. step-up transformers) and associated footprint and connections to realize connection to the medium voltage distribution grid.
Space, footprint, and collateral connection equipment are not particularly challenging for STATCOMs designed for use in transmission systems. In contrast to this, distribution lines are often located in areas that have limited land access (industrial parks, residential neighborhoods or land constrained right-of-ways) or other siting issues that make the construction of a dedicated substation prohibitive from a cost, legal or political standpoint.